Audiometry is the testing of function of the hearing mechanism, including mechanical sound transmission tests (middle ear function), neural sound transmission tests (cochlear function), and speech discrimination ability tests (central integration). Typically, a complete evaluation of a patient's hearing is done by trained personnel using instruments designed specifically for hearing testing. In conventional audiometric hearing testing, an audiometer generates pure tones (single frequencies) to test air and bone conduction. The audiometer includes a pure tone generator, an oscillator for bone conduction testing, an attenuator for varying loudness, a microphone for speech testing, and earphones for air conduction testing. Other hearing tests include auditory brainstem response (ABR), which measures neural transmission time and amplitude from the cochlea through the brainstem.
Pure tone audiometric bone conduction testing is performed by presenting a pure tone to the ear through an oscillator placed on the mastoid and measuring threshold (i.e., the lowest intensity in decibels (dB) at which the pure tone is perceived 50% of the time). For auditory brainstem response (ABR) audiometry, electrodes are placed on the patient's vertex, earlobes, and forehead. Auditory brainstem responses (ABRs) produced in response to air and bone conduction stimuli may provide frequency-specific hearing thresholds. The air and bone conduction ABR thresholds, similar to typical behavioral audiometric testing, provide diagnostic information that differentiates between conductive, sensorineural, and mixed hearing losses. ABR testing can be used to assess patients, such as young children, infants, and difficult to test patients that cannot be evaluated with conventional behavioral audiometric testing.
FIG. 1 is a top, side perspective view of a bone-conduction oscillator 100 as is known in the art. Referring to FIG. 1, there is shown a bone-conduction oscillator 100 comprising a housing 110 and a cable 120. The cable may be operable to provide the bone-conduction stimuli from the audiometer and/or auditory brainstem response (ABR) equipment, for example. The housing 110 can include a detent 112 for attaching to a headband. For example, typical bone-conduction oscillators are commonly placed on a patient using metal headbands. Some researchers recommend using a spring-scale to measure the coupling force of the headband to a head of a patient to control the force applied to the bone-conduction oscillator 100.
In conventional audiometric bone conduction testing and auditory brainstem response (ABR) testing, one concern is that the amount of force applied to the bone-conduction oscillator 100 is consistent and within an appropriate range. The amount of force applied to the bone-conduction oscillator is proportional to the efficiency of the transmission of the stimulus from the oscillator to the bone. Too much pressure, too little pressure, or variations in pressure during the presentation of a stimulus can cause a greater degree of uncertainty in the measurements taken. Coupling the oscillator 100 to a head of an infant using a headband is a commonly suggested clinical method for performing auditory brainstem response (ABR) testing because a force can be applied by the headband and the amount of force can be verified. However, current commercially available headbands for bone-conduction oscillators do not allow one to regulate and monitor static pressure. This becomes an even more difficult problem with the smaller heads of children. Another method used in a clinical setting is to hold the bone-conduction oscillator 100 in place by hand because it is more comfortable for an infant and is faster and less likely to wake the infant than positioning a headband. However, the hand-held method has generally been discouraged due to the potential for the applied force to be outside an appropriate range and/or to vary during testing, resulting in an inconsistent output from the transducer, which can potentially produce inaccurate thresholds.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.